This invention relates to large guns such as guns mounted in tank turrets and, more particularly, to a mechanism for sensing the angular elevation of the gun.
Large guns such as those in tank turrets are usually mounted on a gun trunnion, which in turn is supported on a base. The gun trunnion is essentially a horizontal shaft which allows the gun to be rotated about the horizontal axis to vary the elevational angle of the gun barrel. The gunner operates an elevating mechanism to rotate the gun about the gun trunnion, thereby changing the upward angle of the gun. The azimuthal angle is controlled by rotating the base on which the gun trunnion is mounted.
These two movements of the gun, the elevational and azimuthal movements, are the primary variables available to the gunner to aim the gun. It is therefore vital to know the exact value of the elevation and azimuth angles of the gun.
The elevational angle relative to the base may be determined by a visual estimate. While this is sufficient for some purposes, other situations require that the elevational angle be determined by an instrument whose readout is provided to a fire controller. For example, the aiming of the gun of a tank when the tank is moving, and the base is pitching, requires the ability to read the elevational angle automatically and provide that elevation to a fire-control computer. Gun trunnion-mounted instruments are available to make these elevational measurements and are operable in some circumstances. In other cases, however, such as retrofits of some gun systems found in older tanks and the like, the gun trunnion may not be accessible for attachment of the elevational angular-measurement instrument.
There have been attempts to design measurement instrumentation to automatically determine the elevational angle of a large gun. However, these prior devices have structures which the present inventor has determined yield inaccurate results due to the presence of slip joints in the mechanical linkages between the gun and the readout device. The inaccuracies result in imprecise aiming of the gun.
There is therefore a need for an alternative approach which is usable to accurately measure the elevational angle of a gun trunnion-mounted gun in those cases where the instrumentation may not be attached directly to the gun trunnion. The present invention fulfills this need, and further provides related advantages.
The present invention provides a gun trunnion elevational angular-sensing mechanism which is usable with a gun whose gun trunnion is not readily accessible for direct attachment of the angular-position readout device. The angular-sensing mechanism is highly accurate yet rugged. It accommodates variations between individual gun arrangements, such as those within the turret of a tank.
In accordance with the invention, a gun trunnion angular-sensing mechanism operable with a gun having a gun trunnion comprises an angular-position readout device having an input shaft, which is desirably supported on a bearing structure for stability, and a linkage including two pinned joints and extending between the gun trunnion and the input shaft of the angular-position readout device. The linkage rotates the input shaft proportionately to a rotation of the gun on the gun trunnion, preferably with a unity proportionality constant so that the rotation of the input shaft is exactly the same as that of the rotation of the gun trunnion. Preferably, the angular-position readout device is an angular resolver utilizing an inductive coil, and the linkage is a parallelogram linkage.
More specifically, one embodiment of the gun trunnion angular-sensing mechanism, operable with the gun mounted for elevational rotation on the gun trunnion, comprises an angular-position readout device having an input shaft, and a linkage rotating the input shaft by the same amount as a rotation of the gun trunnion. The linkage comprises a gun trunnion arm affixed at a first end thereof to the gun trunnion and rotating with the gun trunnion, the gun trunnion arm having a gun trunnion-arm length; a control arm parallel to the gun trunnion arm and having a control-arm length equal to the gun trunnion-aim length, the control arm being affixed at a first end thereof to the input shaft of the angular-position readout device; a fixed arm comprising a body which is fixed relative to the gun trunnion and the angular-position readout device, and having a fixed-side length measured between the gun trunnion and the angular-position readout device; and a linkage arm having a linkage-arm length equal to the fixed-side length, the linkage arm being pivotably attached at a first end thereof to a second end of the gun trunnion arm and being pivotably attached at a second end thereof to a second end of the control arm. The pivots are preferably accomplished with double-row, angular contact, ball bearings.
The angular-sensing mechanism of the invention is particularly useful in relation to the guns of tanks that have an arm extending downwardly from the gun trunnion, which may be used as the gun trunnion arm. An example is the M60A3 tank now in service throughout the world. The present approach allows the elevational angle to be sensed automatically and continuously, so that automatic fire control is possible even when the tank is moving.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. The scope of the invention is not, however, limited to this preferred embodiment.